Steam power plant

ABSTRACT

The invention relates to an inventive steam power plant comprising at least one steam turbine and a steam generator. According to the invention, a firing device is located downstream of the steam generator and upstream of the steam turbine and/or downstream of a first turbine phase and upstream of a second turbine phase of the stream turbine in the direction of the stream flow and the steam flow can be heated in a combustion chamber of the firing device by being mixed with a heating gas that can be generated in the combustion chamber.

CROSS REFERENCE TO RELATED APPLICATION

This application is the US National Stage of International ApplicationNo. PCT/EP2003/005123, filed May 15, 2003 and claims the benefitthereof. The International Application claims the benefits of EuropeanPatent application No. 02014453.1 EP filed Jun. 28, 2002, both of theapplications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a steam power plant having at least one steamturbine and a steam generator.

BACKGROUND OF THE INVENTION

In known steam power plants, operating steam for a steam turbine isgenerally generated in a steam generator, the energy contained in a hotgas being released to one or more heat exchangers which are fed withwater, so that operating steam can be generated by heating this water,or which are fed with steam, so that the steam can be superheated bymeans of a said heat exchanger; superheating of this type, in knownsteam turbines, takes place, for example, between a high-pressure stageand a medium-pressure stage of the steam turbine, the steam which leavesthe high-pressure stage being superheated by means of a reheater heatingsurface arranged in the steam generator and being fed to themedium-pressure stage.

This reheating of the steam makes a contribution, for example, toincreasing the efficiency of the steam turbine.

In known steam power plants, thermal energy is supplied in order togenerate and/or reheat steam by means of heat exchanger surfaces whichare arranged in the steam generator and come into contact with a hot gasguided in the steam generator. The heated heat exchanger surfaces inturn release their thermal energy to water and/or steam guided insidethe body formed by a heat exchanger surface. The heating is thereforerealized by means of heat transfer from the hot gas to the heatexchanger surface and from the heat exchanger surface to the medium thatis to be heated.

Since in the heat exchangers which are known from the prior art and areused in steam generators of known steam power plants the energy of a hotgas is transferred to the medium to be heated by means of a material ofthe heat exchanger surface that has been heated by the hot gas, thequantity of energy which can be transferred to the medium to be heated,for example water and/or steam, is limited by the materials propertiesof the heat exchanger surface.

Therefore, in known steam power plants, the permissible steamtemperatures are limited, since the heat exchanger surface whichtransfers the thermal energy cannot be heated to any desired temperaturelevel on account of its material properties and associated thermalloading limits.

Furthermore, the transfer of heat from hot gas to the medium that is tobe heated is subject to a delay caused substantially by the requiredheating time of the heat exchanger surface.

SUMMARY OF THE INVENTION

Therefore, the invention is based on the object of providing a steampower plant having at least one steam turbine and a steam generatorwhich can be used flexibly and in particular overcomes theabovementioned drawbacks of the prior art.

According to the invention, the object is achieved by a steam powerplant, comprising at least one steam turbine and a steam generator, inwhich steam power plant a firing device is arranged downstream of thesteam generator and upstream of the steam turbine and/or downstream of afirst turbine stage and upstream of a second turbine stage of the steamturbine, as seen in the direction of the flow of steam, and the flow ofsteam can be heated in a combustion chamber of the firing device bybeing mixed with a hot gas that can be generated in the combustionchamber.

In this context, the invention is based on the consideration that thetransfer of heat from a hot gas to a medium that is to be heated is lessrestricted compared to the prior art if the transfer of energy to themedium that is to be heated dispenses with the use of a heat exchangersurface.

In the invention, this is achieved by virtue of the fact that the flowof steam which is to be heated is introduced directly into a combustionchamber, where it is mixed directly with the hot gas.

This internal additional firing according to the invention can be useddownstream of the steam generator and upstream of the steam turbine, asseen in the direction of flow of steam, i.e. to superheat live steam, orto superheat steam which has already released some of its energy in aturbine stage and is fed to a further turbine stage after superheatingaccording to the invention.

A steam power plant according to the invention can use higher steamtemperatures than the prior art, which can contribute to an increase inthe efficiency of the steam power plant.

Hydrogen and/or a hydrocarbon, in particular methane, can advantageouslybe fed to the firing device as fuel.

The use of hydrogen as fuel offers the advantage in particular that—ifthe hydrogen, as is generally customary, has been produced by reformingor gasification from a hydrocarbon—carbon dioxide which is produced canbe blocked with relatively little outlay on energy as early as duringproduction of the hydrogen during reforming or gasification of ahydrocarbon, and in this way the formation of an acidic steam mixturewithin the steam turbine and/or other components of the steam powerplant is avoided from the outset.

To achieve particularly successful firing of the combustion chamber, anoxygen-containing gas, in particular pure oxygen and/or air, canadvantageously be fed to the firing device in order to generate acombustion atmosphere.

This embodiment of the invention takes account of the requirement forcombustion of a fuel to be possible only in a suitable combustionatmosphere. Particularly efficient combustion is possible by means ofthe supply of pure oxygen, since this gas, unlike air, does not containany other constituents which may impede combustion and would undercertain circumstances have to be separated off prior to combustion, forexample in an air separation device, in order to create a suitablecombustion atmosphere.

In a further preferred embodiment of the invention, combustion productswhich are produced can be removed from the flow of steam by means of acondenser connected downstream of the steam turbine.

Virtually all combustion processes form combustion products, whichgenerally have to be dissipated, since, in particular after a prolongedoperating time, they may accumulate in the combustion chamber or othercomponents and restrict the functioning thereof.

If, in a steam power plant according to the invention, for example,hydrocarbon is burnt as fuel in an atmosphere of pure oxygen, at leastthe combustion products water and carbon dioxide are formed. Thesecombustion products are entrained by the flow of steam and are fed tothe condenser. In known steam power plants, there is generally already acondenser, which means that within the context of the invention aseparate condenser suitable for removal of the combustion products doesnot necessarily have to be provided.

During the cooling of the steam which contains the combustion productsas a water/carbon dioxide mixture, the water fraction is substantiallycondensed and what remains is virtually pure, gaseous carbon dioxidewhich can be removed from the condenser and, for example, stored.

As has already been mentioned, if hydrogen is used as the fuel which isproduced by reforming or gasification of a hydrocarbon, carbon dioxidewhich is produced can be removed even before the fuel is introduced intothe firing device, so that in this case scarcely any carbon dioxide isformed as combustion product during the combustion.

The internal additional firing which is realized by means of the firingdevice of a steam power plant according to the invention can be madeavailable very quickly during operation of the steam turbine. For thispurpose, it is merely necessary to ignite fuel which has been introducedinto the combustion chamber; in particular, the heat-up times of knownheat exchanger surfaces are eliminated.

Furthermore, a steam power plant according to the invention offers theadvantage that combustion products and/or exhaust gas do not necessarilyhave to be discharged from the combustion chamber by means of a separatedischarge device, since they can be entrained by the flow of steam andremoved elsewhere in the steam circuit, for example the abovementionedcondenser. Moreover, the invention makes it possible to reach a highersteam temperature without having to change the design of the steamgenerator.

A steam power plant according to the invention can in particular also beused to provide energy at peak load times or to boost the mainsfrequency of an electrical energy supply network; a steam power plantaccording to the invention offers the possibility of rapid power controland can be used very flexibly.

BRIEF DESCRIPTION OF THE DRAWING

The following text provides a more detailed explanation of an exemplaryembodiment of the invention. In the drawing:

The FIGURE shows a steam power plant according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The FIGURE illustrates a steam power plant 1 according to the invention,which comprises a steam turbine 3 coupled to a generator 21, as well asa steam generator 5.

The steam turbine 3 is of three-stage construction and includes a firstturbine stage 11, a second turbine stage 13 and a third turbine stage15, which are respectively designed as high-pressure stage,medium-pressure stage and low-pressure stage.

In the present exemplary embodiment shown in the FIGURE, the steamgenerator 5 is a boiler fired by means of coal 27, to which combustionair 29 is fed in order to maintain the coal firing.

A heating surface 37 is arranged in the region of the hot end of thesteam generator 5, and a reheater heating surface 35 is arranged in alower-temperature region of the steam generator 5.

The heating surface 37 is used to heat feedwater 24 from a feedwatervessel 23 in the steam generator 5 in such a manner that operating steamcan be fed to the first turbine stage 11.

After partial expansion in the first turbine stage 11, the steam isreheated by means of the reheater heating surface 35. A flow of steam 17emerges from the reheater heating surface 35 in direction 9 and is fedto a firing device 7. In the process, the flow of steam 17 is heated ina combustion chamber 19 by means of a fuel 33 and addition of oxygen 31,with the flow of steam 17 being mixed in the combustion chamber 19 withthe hot gas which is formed in the combustion chamber 19 during thecombustion of the fuel 33.

Therefore, the transfer of heat from the hot gas to the flow of steam 17takes place directly by mixing, without a material, for example a heatexchanger surface, being provided for heat exchange.

As an alternative to oxygen 31, it is also possible to use air togenerate a suitable combustion atmosphere, the air being split intooxygen and residual gas by means of an air separation device ifappropriate before it is introduced into the combustion chamber.

The fuel 33 used may, for example, be a hydrocarbon, in particularmethane, or hydrogen.

The flow of steam 17 which has been heated by means of the firing device7 is fed to the second turbine stage 13, where it converts at least someof the energy which it contains into mechanical work. The steam whichhas been further expanded in this way leaves the second turbine stage 13and is fed to the third turbine stage 15, where the energy which isstill present in the steam is converted as fully as possible intomechanical energy.

The expanded steam leaves the third turbine stage 15 as a water-steammixture and is fed to a condenser 25, where the steam fraction which isstill present is condensed to form water.

This water which collects in the condenser 25 is fed to the feedwatervessel 23 as condensate 26.

Combustion products 39 which are formed during combustion in thecombustion chamber 19 of the firing device 7 can be removed from thecondenser 25.

Since the combustion takes place within the flow of steam 17 in thecombustion chamber 19, the combustion products 39 are entrained by theflow of steam 17 in the steam circuit and according to this embodimentof the invention are removed from the condenser 25.

If the fuel 33 burnt is, for example, a hydrocarbon together with oxygen31, the combustion products 39 comprise water and carbon dioxide. Thiswater/carbon dioxide mixture is entrained by the flow of steam 17 andcan be removed from the condenser 25, since the water fraction issubstantially condensed during the cooling of the water/carbon dioxidemixture and virtually pure gaseous carbon dioxide remains as gas whichcan then be transported away and, for example, stored.

Water as combustion product of course does not usually have to bedischarged, but rather can be fed to the feedwater vessel 23 as aconstituent of the condensate 26.

1-4. (canceled)
 5. A steam power plant, comprising: a steam turbinehaving a first turbine stage and a second turbine stage; a steamgenerator; a firing device arranged downstream of the steam generatorand upstream of the steam turbine as seen in the direction of a flow ofsteam; and a combustion chamber associated with the firing device suchthat and the flow of steam can be heated in the combustion chamber bybeing mixed with a hot gas that is generated in the combustion chamber.6. The steam power plant as claimed in claim 5, wherein the firingdevice is fueled by methane.
 7. The steam power plant as claimed inclaim 5, wherein a firing device is arranged downstream of the firstturbine stage and upstream of the second turbine stage and the flow ofsteam is heated in a combustion chamber of the firing device by beingmixed with a hot gas that is generated in the combustion chamber.
 8. Thesteam power plant as claimed in claim 5, wherein an oxygen-containinggas, or air, is fed to the firing device in order to generate acombustion atmosphere in the combustion chamber.
 9. The steam powerplant as claimed in claim 5, wherein an oxygen-containing gas, and air,is fed to the firing device in order to generate a combustion atmospherein the combustion chamber.
 10. The steam power plant as claimed in claim8, wherein an oxygen-containing gas is pure oxygen.
 11. The steam powerplant as claimed in claim 5, wherein combustion products produced areremoved from the flow of steam by a condenser connected downstream ofthe steam turbine.